Under floor insultation in bedroom over a garage

We'd need to see the job. Yo didn't say where. The condensation is appearing is it on the walls and the ceiling windows all the floor? We need to understand what type of what you have to have a cavity? Are they single break? How is the space heater? Is it single-storey or in other rooms above your space? Is it just a flat roof above this area or is it a loft for the cavity? Sorry about all the questions but as you can see there's a lot to consider. If however you already know the answers to the above. And there are no issues with any of these areas then I woul then look at the floor. I with the need to know the head height of the room as it is possible to insolate floor. I would need to know that the floor construction and how are you heat the space D is electric radiators wet system would burner or no heating at all? It's very important to get the answers to all of these questions to solve your in order to solve your problem properly. The bit like going to the doctors with the pain and the doctor just giving you some pills or spending time diagnosing the real problem and treating it accordingly. Feel free to contact me via my builder. Kind regards Dave